encrypt _ decrypt kata

function encrypt(text, n) { 
  if ( !text || text.length <= 1) return text;
  let result = text.split('');
  for(let i = 0; i < n; i++) {
    let odds = [];
    for(let i = 0; i < result.length; i++) {
      odds = odds.concat(result.splice(i, 1));
    }
    result = result.concat(odds);
  }
  return result.join("");
}

function decrypt(encryptedText, n) {
  if ( !encryptedText || encryptedText.length <= 1) return encryptedText;
  let encryptedArr = encryptedText.split('');
  let firstPart = [];
  let middle = countMiddle(encryptedArr);
  console.log(middle);
  let decrypted = [];
  
  for (let i = 0; i < n; i++ ) {
    firstPart = encryptedArr.splice(middle, encryptedArr.length - middle);
    for (let i = 0; i < encryptedText.length; i++ ) {
      isOdd(i) ?
        decrypted = decrypted.concat(encryptedArr.splice(0, 1)): 
        decrypted = decrypted.concat(firstPart.splice(0, 1))
    }
    encryptedArr = decrypted;
    decrypted = [];
  }
  
  return encryptedArr.join("");
}

function isOdd(num) {
  return num % 2 !== 0;
}

function countMiddle(arr) {
  return Math.floor(arr.length / 2 );
}